One of our readers wrote in asking for clarification from Dr. Macrina: “Dr. Macrina indicated it could be any of several factors – better nourishment, higher body weight and some even suggest exposure to chemicals. Does Dr. Macrina mean chemicals like pesticides and herbicides?”

Exposure to chemicals and their effects on onset of puberty currently is a very active area of research. These chemicals include those found in pesticides (DDT, DDE, endosulfan, for example), or plastics used as food containers (BPA), and other plastics including those manufactured for flame retardance (BPP). This is by no means a complete list, but the concern is that these chemicals are structurally similar to estrogen. If they bind to the estrogen receptor in the body, these chemicals might mimic or block the actions of estrogen. Chemicals such as DDT were banned from use decades ago but are still present in the environment. Bisphenol A (BPA) has been shown to leach out of plastic containers especially with repeated use. However, it is difficult to quantify individual exposure to these chemicals and correlate that with outcomes like earlier age at puberty. Some researchers report earlier onset of puberty when animals are given high doses of these chemicals, but that is not the same as low-dose environmental exposure. Also, many of these chemicals have been in the environment since the 1960s, yet the age of puberty continues to decrease. A recent study examined girls who lived near or far from agricultural regions where pesticides were used. The scientists could not detect a difference in blood levels of the pesticide chemicals.

In my original blog, I was referring to any chemicals that might mimic the actions of estrogen in the body. There are many conflicting studies, and it is not clear if the level to which people are exposed contributes to earlier onset of puberty. Based on the historical data before these chemicals were used, body weight consistently was around 100 pounds at the onset of puberty. The fact that it is still around 100 pounds implies that body weight has more of an influence on timing of puberty than typical exposure to these chemicals. However, it is important to understand how these chemicals act in the body, and research in this area continues.